EAST Lab -  University of Michigan
DFE World: Design & the Global Environment
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 Central Campus Air Quality Model Line Sources Effective Stack Height Mixing Height & Inversions Model Output Sensitivity Analysis

# Effective Stack Height

Plumes rise vertically from a smokestack before starting to disperse according to the Gaussian model (see figure below).  Therefore, because of the plume rise, the centerline of the Gaussian model is higher than the height of the stack.  The “effective stack height”, which is stack height plus vertical plume rise, is used in the Gaussian model for more accurate calculations of pollution concentration from a point source.

Plume Rise and Effective Stack Height

Calculating Effective Stack Height Wind Speed

The surface wind speed is different at the effective stack height, which is used in the Gaussian model.  To determine the effective stack height wind speed, UH, use the following equation and table.

Where:

• Ua = wind speed at altitude Za, m/s

• H = effective stack height, m

• Za= height above surface, m (usually 10 meters)

• p = exponent is a function of atmospheric stability class

 Description Exponent p A Very unstable 0.15 B Moderately unstable 0.15 C Slightly unstable 0.20 D Neutral 0.25 E Slightly Stable 0.40 F Stable 0.60